Graphic materials incorporating microsphere distributions for the presentation of visual information



June 11, 1968 G. ALTMAN 3,388,027

GRAPHIC MATERIALS INCORPORATING MICROSPHERE DIsTRIBUTIoNs FOR THEPRESENTATION oF VISUAL INFoRMATIo Filed March 2, 1966 Syfawr efj/assspheres hau/ig @Iver .Su/forf- United States Patent O S Claims. (Cl.161-4) 10 .en-a. caf

ABSTRACT 01T THE DISCLOSURE Visual products for the display of imagesare provided with strata of microspheres of selected optically operativecharacteristics. The distribution of the microspheres, by virtue oftheir small size, area concentration, refractive index and opticallyclear bond to their support, operates to control ditlused andconcentrated light for projection and observation.

Background and summary of the invention The present invention relates tographic materials that both are to be viewed by direct observation andare to be imaged by projection. More particularly the present inventionrelates to graphic sheets of a type that is characterized by adistribution of minute reiracting optical spheres, which preservepleasing diffusion of light transmitted from the sheet directly to theeye but which ensure eiiicient utilization of light projected from thesheet to a viewing screen or the like.

The present application is a continuation-in-part of U.S. patentapplication No. 249,351, tiled l an. 4, 1963, now Patent No. 3,269,839,issued Aug, 30, 1966, in the name of the applicant hereof for OpticalProducts, Processes and-Devices. The disclosure of this patent, which isincorporated into the present disclosure by reference, illustrate usesfor which materials of the present invention are intended.

A primary object of the present invention is to provide selected graphicmaterials of the foregoing type, by which directly viewed diiluse lightmay be effectively produced by any randomly selected source but by whichprojected concentrated light may be eliectively utilized for imageformation at a distance. In such applications as printing with ink,photography with develop-able particles, etc., it is advantageous toselect the optical constants of the refracting spheres, particularlydiameter and index 0f refraction, for optimum observation vs. projectionrelationships. In such applications, it is important that the refractingsphere distribution macroscopically provide a iiux cross section that ineffect is an optical continuum.

Other objects of the present invention are: to coat the surface ofaluminum foil, via an optically clear cement, with particularly selectedminute glass Spheres that iadjacently contact each other in order toprovide a refluxreflecting graphic sheet; to relate the opticalconstants of such minute glass spheres to the visual subject matter ofstrata in Contact therewith and predeterminedly spaced therefrom; toprint with ycolored minute glass spheres of the foregoing type; toenhance the projection capabilities of a translucen-cy; and to provide asimple scribing technique that is adapted for direct diffuse observationand projection image production.

Other objects of the present invention will in part be obvious and willin part appear hereinafter.

The invention accordingly comprises the products and relationships amongtheir components, which are exempli- 70 tied in the following detaileddisclosure, the scope of which will be indicated in the appended claims.

Brief description of drawing For a fuller understanding of the natureand objects of the present invention, reference should be had to thefollowing detailed description, taken in connection with theaccompanying drawings, wherein:

FIG. 1 is an exaggerated cross sectional view of an overhead projectionproduct embodying the present invention;

FIG. 2. is an exaggerated cross sectional view of a photographicallydeveloped product embodying the present invention;

FIG. 3 is an exaggerated cross sectional view of a multicolor printedproduct embodying the present invention;

FIG. 4 is an exaggerated cross sectional view of a translucentprojection product embodying the present invention; and

FlG. 5 is an exaggerated cross sectional view of a projection scribingproduct embodying the present invention.

Detailed description Generally, the products illustrated herein utilizegl-ass microspheres of optical clarity, of which by Weight range indiameter from 30 to 1 micron or below, and which have an index ofrefraction that ranges in various applications from 1.5 to 2.6.Especially suitable glass microspheres of the foregoing type are sold byCataphote Corporation, Jackson, Miss., under the trade designation No.4000 Extra Fine Uni-Spheres7 a product composed of high-grade opticalcrown glass, soda-lime type, with silica content not less than 60%, andhaving an ND ranging from 1.5 to 1.9. Also suitable are glassmicrospheres of like small diameter having analagous compositions exceptfor the addition of optimum high concentrations of lead or titanium, andhaving an ND ranging from 1.9 to 2.6. These microspheres are adhered tothe illustrated substrates by an optically clear polymer, for example,gelatine, which has been applied from a suitable polar solvent such aswater, linseed oil which has been applied from a suitable organicsolvent such as turpentine or methyl rnethacrylate which has beenapplied from a suitable organic solvent such as toluene. The areaconcentration of the microspheres is maximized to achieve a coveringpower preferably of at least 90%, there being a range of largermicrospheres which are virtually in contact with each other, i.e., nolmore than 10% of their average diameter apart, a range of smallermicrospheres which cover the interstices defined by three or moreadjacent larger microspheres, and in some cases additional layers oilarger or smaller microspheres to cover interstices in other layers. Thesubstrate to which the microspheres are applied is a continuous thinlayer, preferably at most 0.0011 inch, of a high (i.e. at least 90%)reliectance metal, such as aluminum or silver, which has been depositedon or laminated to a suitably thick (eg. 0.0005 to 0.05) paper such asbaryta or polymer such as cellulose acetate or cellulose nitrate. Theoverall selection of materials is such that -a very large proportion ofdirective incident light is returned toward its source with controlleddispersion. rl'he minimization of dispersion in the reilex reilectedlight cone, which is characteristic of trac control reilex reflectivematerials well known in the prior art, is not a primary consideration inthe cross of the present materials because the present materials are tobe used in an optical system that intercepts the major proportion of theintegrated ux cross section of a reflex reilected light cone that isbroader than that needed by the prior materials. ln order to achieveproper index of refraction relationships between the glass microspherestratum and other strata of the product of the present invention, theglass microsphere stratum, in various forms, includes two or moresubstrata of glass microspheres of different N@ or includes glassmicrospheres of different ND in predeterminedly interspersed relation.An important feature of the present materials is that the naturaldiffraction and aberration of the glass microspheres ens-ure sufficientscattering of randomly incident light to produce a white (orpredeterminedly colored) appearance when viewed normally. The followingexamples of materials of the present invention are in reference to thefigures of the drawing.

FIGURE 1 shows open face la er of glass microspheres 10 bonded to areflective metal coil 12 which is laminated to a paper support 14.Microspheres ltl range in diameter from 1 to 3() microns and have anindex of refraction, ND=1.9. The outer hemispheres of microspheres l@are free of adhesive and the inner hemisphcres are bonded to foil 12 bya clear epoxy adhesive stratum having a depth of molecular dimension.Foil 12 in turn is `bonded by a similar adhesive to paper support 14,which for example is composed of suitable kraft sheeting. The arangementis such that in excess of 90% of the area of foil 12 is covered bymicrospheres and the uncoated interstices serve as light conduits alsoby virtue of the reflectivity of the side surfaces of the microspheresthat bound the interstices. The product of FIG. 1 is suitable for directmarking for use in an episcopic projector.

In a modification of the product of FIG. 1, a photographic transparencyor other graphic representation is interposed at 16 between microspherelayer ltland foil 12. In various forms, the photographic transparency isa developed silver halide, diazo, ferrie, photopolymeric orphotothermographic print. This representation is suitable for bothdirect observation and episcopic projection.

FIG. 2 illustrates, in lam-inated sequence, a photographic print stratum18, an optical spacing stratum 20, a glass microsphere stratum 22, areflecting metal stratum 24 and a paper support stratum Z6. Photographicprint stratum 13 is a gelatino silver print. Spacing stratum is composedof gelatine and is sufficiently thick, e.g. .05 inch, toypredeterminedly defocus glass microsphere stratum 22 when photographicprint stratum 18 is in focus in an episcopic projector. The glassspheres are of titanium or lead glass having an ND ranging from 1.9 to2.6. This high ND differs from the ND of outer gelatine stratasufficiently to ensure predetermined refraction.

FIG. 3 illustrates, in laminated sequence, a three color halftoneprinted stratum 28, a reflecting aluminum stratum 30 and a paper support32. This product is formed by an ordinary multicolor printing presshaving rollers which first apply metal layer 30 (either as foil as flakein a binder) to paper stratum 32 and then apply successive halftonecoats of cyan ink 34, magenta ink 36 and yellow ink 38. As shown each ofthese inks includes crystal clear glass microspheres in a dyed matrix,the latter being composed of conventional viscous linseed varnishcontaining an appropriate chromophoric dye. In an alternative form ofthe product of FIG. 3, the glass spheres are colored and the varnish isclear. This form of the invention contemplates a two color process inwhich the only glass spheres are generally red and generally whiteappropriately representing color separation scenes that are generallyblue and generally red.

FIG. 4 illustrates a clear plastic sheet 40 composed of gelatin or otherilow index of refraction material, on which is disposed a distributionof microspheres 42 composed of glass having a relatively high index ofrefraction, preferably ranging from 1.8 to 2.6. Adhesion between theglass microspheres and the plastic sheet is effected by an aqueousmixture of 50%-50% gelatine and glycerine. This product is useful as asupport for a photographic representation to be projected diascopicallyor as a rear projection screen.

FIG. 5 illustrates a normally opaque layer 44 that may be easily clearedwhen desired, a metal layer 46 and a paper support 48. Metal layer 46and paper support 48 are analagous to the counterparts in FIGS. 1, 2 and3. Normally opaque layer 44 is composed of a polar acting dye whichclears in acid or alkali, for example, phenophthaline dispersed in agelatine matrix. On the surface of opaque stratum 44 are shown in driedmicrosphere ink originally containing a dispersion of microspheres, ofeither high or low index of refraction, in an aqueous alkaline gelatinesolution. When this ink is written onto opaque stratum 44, alkalineclearing takes place as at 50 and the glass microspheres are retained inposition as at 52 to provide localized reex reflecting regions havingdesired alphanumeric or symbolic configurations.

The present thus provides a variety of products that may be viewedcomfortably in terms of diffuse light and may be projected effectivelyin terms of concentrated light. Since certain changes may be made in theabove disclosure without departing from the scope of the inventionherein involved, it is intended that all matter contained in theforegoing description or illustrated in the accompanying drawing beinterpreted in an illustrative and not in a limiting sense.

What is claimed is:

1. A graphic product for direct observation in terms of diffuse lightand for image projection in terms of concentrated light, said graphicproduct comprising, in laminated sequence, a paper-like backing stratum,a continuous metal reflecting stratum and a glass microsphere stratum,said microsphere stratum being composed of a multiplicity ofmicrospheres which cover at least of any selected macroscopic area ofsaid metal reflecting stratum, at least 90% of said microspheres beingless than 30 microns in diameter, said multiplicity including a range oflarger microspheres defining interstices thereamong and a range ofsmaller microspheres filling said interstices, adjacent microspheres ofsaid multiplicity being substantially in contact with each other, thebond between said multiplicity of microspheres and said metal reectingstratum being optically clear in order not to obstruct access of lightthrough said microsphere stratum to said metal reflecting stratum,substantially all of said multiplicity of microspheres beingcharacterized by an outer optical surface remote from said metalreflecting stratum and an inner optical surface contiguous with saidmetal reflecting stratum, said outer optical surface being free toreceive and transmit light incident on said microsphere stratum, saidmultiplicity of microspheres by virtue of their specified size, areaconcentration and optically clear bond to said metal reflecting stratumoperating to diffuse randomly incident light for direct viewing and toconcentrate directed light for episcopic projection.

2. The product of claim 1 wherein a developed photographic stratum islaminated to the outer face of said microsphere stratum.

3. The graphic product of `claim 2 wherein said photographic stratumcontains silver.

4. The graphic product of claim 1 wherein a visual presentation stratumis interposed between said microsphere stratum and said reectingstratum.

5. The graphic product of claim 1 wherein said microspheres areassociated in different regions and characterized -by different colors.

6. The graphic product of claim 5, wherein a generally opaque maskingstratum is interposed between said refleeting stratum and saidmicrosphere stratum, said microsphere stratum having restricted andseparated concentrations of microspheres, said masking stratum beingcleared in the vicinity of concentrations.

7. A product comprising an optically clear support sheet, a glassmicrosphere stratum carried thereby, and a bonding material joining saidmicrosphere stratum to said support sheet, said microsphere stratumbeing composed of a multiplicity of microspheres which cover at least90% of any selected macroscopic area of said support sheet, said bondingmaterial `being optically clear,

at least 90% of said microspheres being less than 30 microns indiameter, the index of refraction of said microspheres beingsubstantially higher than the index of refraction of said support sheet,said multiplicity of microspheres by virtue of their small size, areaconcentration, index of refraction and optically clear bond to saidsupport sheet operating to substantially di'use randomly incident lightfor direct viewing but to substantiallytransmit concentrated light forprojection.

y8. The graphic product of claim 1 wherein the index of refraction ofsaid microspheres is at least ND=1.9.

References Cited UNITED STATES PATENTS Palmquist 117-35 X Phillippi41-33 Porth 117-35 Palmquist et al. 106-193 Searight 106-193 NORMAN G.TORCHIN, Primary Examiner.

R. H. SMITH, Assistant Examiner.

